Relay is OMRON MY2F -12DC, you'll need two.
Can these be mounted under the hood on the firewall? I was looking, and I was wrong, my brake wire doesn't come into the cab. I was thinking that since my turn signals and brake wires are all right there within inches of each other I could just mount the relays there.
I assume you brought extended your brake wires back into the cab. Did you cut your signal wires in the cab or under the hood and then bring them back thru the cab.